The phenomenon of size tunable fluorescence is rooted in quantum confinement. At the nanoscale, the motion of electrons is confined to such a small volume that quantum mechanical effects become significant. When the dimensions of a material are reduced to the order of the exciton Bohr radius, the energy levels of the electrons are quantized. This means that the energy gap between the conduction band and the valence band increases as the particle size decreases, resulting in the emission of higher energy (shorter wavelength) light.
